The Sun compared to some smaller stars. The Sun (bottom) is a yellow dwarf with a diameter of about 1.4 million km. But most stars are far smaller. The most common stars in the universe are red dwarves, such as Proxima Centauri (centre left). It is only 12% of the diameter of the Sun. White dwarves, such as Sirius B (centre right), are much smaller and denser still, at around 0.8% of the diameter of the Sun - comparable to the Earth. And even smaller are the neutron stars (seen in the zoom). At 20 km across, they are the smallest 'stars' in existence.